Erik Prince, a private military contractor and prominent supporter of President Trump, is working with Haiti’s government to conduct lethal operations against gangs that are terrorizing the nation and threatening to take over its capital.

Mr. Prince, the founder of Blackwater Worldwide, signed a contract to take on the criminal groups that have been killing civilians and seizing control of vast areas of territory, according to senior Haitian and American government officials and several other security experts familiar with Mr. Prince’s work in Haiti.

Haiti’s government has hired American contractors, including Mr. Prince, in recent months to work on a secret task force to deploy drones meant to kill gang members, security experts said. Mr. Prince’s team has been operating the drones since March, but the authorities have yet to announce the death or capture of a single high-value target.

Security experts said Mr. Prince has also been scouting Haitian American military veterans to hire to send to Port-au-Prince and is expected to send up to 150 mercenaries to Haiti over the summer. He recently shipped a large cache of weapons to the country, two experts said.

The Haitian government is awaiting the arrival of arms shipments and more personnel to step up its fight against the gangs.

American officials said they were aware of Mr. Prince’s work with Haiti’s government. But the full terms of the Haitian government’s arrangement with Mr. Prince, including how much it is paying him, are unknown.